This application is based upon and claims benefit of priority of Japanese Patent Application No. Hei-11-158010 filed on Jun. 4, 1999, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a rotational power converter that converts an output of an internal combustion engine into a driving force of a hybrid electric vehicle driven by combination of the engine and an electric power.
2. Description of Related Art
A device for driving a hybrid electric vehicle by combination of an engine and a battery is disclosed in JP-A-8-251710. In this device, an electrical coupling for changing a rotational speed of the engine and an electric motor for assisting a driving torque of the vehicle are provided. The device helps to save a driving energy and to reduce harmful exhaust gas. In this device, however, it is necessary to provide an electric feeder composed of brushes and slip-rings for supplying electric current to the motor. The electric feeder is often detrimental to durability or reliability of the device.
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide an improved device for converting an engine output to a driving power of a hybrid vehicle in a controlled manner, and more particularly to provide a reliable rotational power converter having no electric feeder.
The rotational power converter of the present invention includes a cylinder-shaped housing, a first stator, a first rotor, a second rotor and a second stator, those stators and rotors being all disposed in the cylinder-shaped housing. The first rotor is connected to an output shaft of an internal combustion engine and is driven by the engine, while the second rotor is connected to driving wheels of an automotive vehicle through reduction gears and supplies rotational power to the driving wheels. Electric power is supplied to windings disposed in both stators from a DC battery through respective inverters.
The first stator including a three-phase winding is fixed in the housing along the longitudinal center axis of the housing. A rotating magnetic field is generated in the first stator by supplying excitation current to the three-phase winding. The first rotor is rotatably supported in the housing, surrounding the first stator, and is driven by the engine. The second rotor is also rotatably supported in the housing, surrounding the first rotor, and is connected to the deriving wheels to supply rotating power thereto. The second stator having a winding is fixed in the housing surrounding the second rotor. A magnetic field is generated in the second stator by supplying electric current thereto from the battery through the inverter.
Both the first and second rotors are placed under the influence of the rotating magnetic field generated in the first stator. When the first rotor is rotated by the engine, rotational power is electromagnetially transferred to the second rotor which drives the driving wheels of the vehicle. The rotational power of the second rotor is adjusted by controlling electric current supplied to the three-phase winding of the first stator. The battery supplies power to the first stator winding or receives power therefrom according to the amount of rotational power of the second rotor. The second rotor is also placed under the influence of the magnetic field generated in the second stator. Accordingly, the battery supplies power to the second stator winding or receives power therefrom according to the rotational power of the second rotor. Thus, the driving force supplied to the driving wheels from the second rotor is controlled or adjusted by controlling the electric current supplied to both stators.
Since the electric current is supplied only to the first and second stators, not to the rotors, in the rotational power converter of the present invention, there is no need to provide an electric feeder composed of slip-rings and brushes. Therefore, the converter can be made smaller in size, and its reliability is improved.
The positions of the first rotor and the second rotor in the housing may be reversed, so that the second rotor is disposed closer to the center axis of the housing. It is also possible to divide the second rotor into two portions connected in tandem and to place them along the longitudinal center line of the housing.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiments described below with reference to the following drawings.